Inflatable structural members



June 16, 1964 J. T- SCURLOCK INFLATABLE STRUCTURAL MEMBERS Filed June 2, 1960 United States Patent 3,137,307 INFLATABLE STRUCTURAL MEMBERS John T. Scurlock, Shreveport, La. (6209 Schouest St.,

Metairie, 1.2.), assignor of fifteen percent to Ralph N.

Jackson and fifteen percent to Stephen B. Lemann, both of New Orleans, La.

Filed June 2, 1960, Ser. No. 34,604 20 Claims. (Cl. 135-1) This invention relates to air supported frames and, in particular, to pressurized air columns used as structural supports. The application of an air supported structure is valuable because it can be used as a temporary, portable, lightweight, and quickly erected shelter. Also it provides long, unsupported, and clear spans not normally possible by rigid material.

Prior structures of this type have apparently been limited to short spans. Also limitations due to curvature of the inflatable tubes were encountered.

The object of this invention is to provide structural members that are governed by the laws of structural engineering so that a unit may be fabricated most ideally.

A particular object of this invention is to specify proper fabrication of the bends to follow proper engineering principles.

Another object of this invention is to specify fabrication by sewing and the insertion of an airtight'film bag as a separate item. This allows complete freedom in fabrication without increasing the possibility of leaks.

Another object is to provide indefinitely long, unsupported, clear spans by following proper engineering principles and proper fabrication methods.

Another object is to provide a structure that is extremely rigid and can be used as a cantilever structure.

A portion of this specification specifically refers to parallel adjacent air columns. Y

These and other objects will become more apparent when specifically covered in the following description to be read in view of the drawings, in which:

FIGURE 1A shows the general design of the novel expanded bend or corner of the present invention;

FIGURE 1B illustrates the reinforced bend orcorner of a rigid or steel beam;

FIGURE 2 shows parallel air columns forming a particular structure; and 7 FIGURE 3A and 3B illustrate various means to obtain access to the inner airtight bag for purposes of repair.

FIG. 1A is a side showing of the general design of the novel corner 10. In essence, a corner is an expanded tube 12 on the inner side 14 serving the same function as a gusset plate used in steel frames, as shown in FIGURE 1B. When the bend is viewed from without at its inner side 14, the tube 12 is convex along a portion of its length. That is to say, tube 12 arches toward the viewer, rather than away from the viewer as illustrated by the dotted line which represents the prior art straight corner. The graph in FIGURE 1A shows how the moment capability of this expanded corner varies with the longitudinal location along the tube. Ideally, the tube or casing 12 should be fabricated of a high tensile strength nylon coated fabric.

By the use of a polyethylene film bag 16 with a minimum diameter larger than the maximum cross section of the externally fabricated nylon tube 12, fabrication of any curvature, the joining of any tubular structure, and terminal or access points can be done without meeting critical dimension requirements and still not increase the possibility of an air loss failure when the column is pressurized.

By following practical limitations as to straight runs of each particular section of a column, clear spans of almost any reasonable length can be designed.

FIGURE 2 shows adjacent air columns connected along their lengths to one another which provide highly rigid air supported structures. These adjacent columns provide extremely stable covers in their plane. Two important re- The weighted base columns seek a central depth in the water sincethe ballast is counteracted by the buoyant force exerted by the pressurized base columns. As can be seen in FIG. 2, anchoring at the left end will exactly hold the right end in an almost fixed position although it is completely free to move except for the strength provided by the adjacent air column. The wind from the left end must act against the same forces. Wind from either side must be counteracted by guy wires to the sides, or alternatively,.there can be low pitched columns going from side to side in place of the high A arch, i.e., the elimination of the large angle in the center of the column. The above specifications and drawings describe the particular purposes of the invention, but it is obvious that various minor changes can be made without departing from the scope of the invention. Of primary concern of this invention is the econom of fabrication andthe convenience of application as to inflation equipment available. In view of this, air column structures are designed based on commonly available air supplies that are most economical. Sinceleaks may occur at remote locations, extreme consideration has been given this problem, as shown in FIGURES 3A and 3B. Specifically, slits 28 and laced openings 30 in the nylon fabric material 12 are provided so that there is quick access to any leak occurring in the inner air tight bag. 'In FIGURE 3A, a fold back sleeve 32 takes stress around the circumference of the tube 12 in the neighborhood of slits 28, yet gives easy access to the inner fihn bag for leak repair. The column takes a longitudinal stress, i.e., parallel to slit 28, without difliculty. The use of an inserted airtight filrn bag that will take ordinarily available adhesive tape allows, quick, positive and permanent repairs .in the field. I

I claim:

1. An inflatable structural member which comprises an elongated tube made of flexible and substantially nonelastic material which has at least one bend fabricated in its length such that said tube is expanded in circumference at said bend, at least on the inner side thereof whereat said'tube defines a convex surface along a portion of its length as viewed from without, to thereby increase the bending moment capability of said member, where said bent tube is adapted for inflation to a pressure sufficient to make it rigid.

2. The invention according to claim 1 wherein said tube material is nylon coated fabric of high tensile strength. V

3. An inflatable structural member comprising:

(a) an elongated tubular casing made of flexible and substantially non-elastic material which has at least one bend fabricated in its length such that said casing is expanded in circumference at said bend, at least on the inner side thereof whereat'said casing defines a convex surface along a portion of its length as viewed from without, to thereby increase the bending moment capability of said member; and

(b) a sealed bag made of flexible and gas tight material inserted within said casing and which extends the length thereof, Where said bag is adapted for inflation to a pressure sufiicient to press it outwardly against the entire interior surface of said bent casing to make the latter rigid.

4. The invention according to claim 3 wherein said bag material is polyethylene film.

5. The invention according to claim 3 wherein said casing material is nylon coated fabric of high tensile strength.

6. The invention according to claim 3 wherein said bag material is polyethylene film and said casing material is nylon coated fabric of high tensile strength.

7. The invention according to claim 3 wherein the uninfiated circumference of said bag at any position along its length is greater than the circumference of said casing at the corresponding position.

8. The invention according to claim 7 wherein said bag material is polyethylene film and said casing material is nylon coated fabric of high tensile strength.

9. An inflatable structural member which comprises a plurality of parallel elongated tubes made of flexible and substantially non-elastic material which are adjacently disposed in the same planes and connected together along their lengths with at least one bend fabricated in said connected lengths such that each tube is expanded in circumference at said bend, at least on the inner side thereof whereat each said tube defines a convex surface along a portion of its length as viewed from Without, to thereby increase the bending moment capability of said member, where each said bent tube is adapted for infiation to a pressure suflicient to make the bent structural member rigid.

10. The invention according to claim 9 wherein said tube material is nylon coated fabric of high tensile strength.

1 1. The invention according to claim 9 wherein at least one of said tubes is provided with means at both ends to anchor it to a foundation.

12. The invention according to claim 11 wherein said tube adapted for anchoring is positioned at one terminus of said plurality of parallel connected tubes.

13. An'inflatable structural member comprising:

(a) a plurality of parallel elongated tubular casings made of flexible and substantially non-elastic material which are adjacently disposed in the same planes and connected together along their lengths with at least one bend fabricated in said connected lengths such that each casing is expanded in circumference at said bend, at least on the inner side thereof whereat each said casing defines a convex surface along a portion of its length as viewed from without, to thereby increase the bending moment capability of said member; and

(b) a plurality of flexible and gas tight bags each inserted within a respective one of said casings and which extends the length thereof, where all of said bags are adapted for inflation to a pressure sufficient" to press them outwardly against the entire interior surface of their bent casings to make the bent structural member rigid.

14. The invention according to claim 13 wherein said bag material is polyethylene film.

15. The invention according to claim 13 wherein said casing material is nylon coated fabric of high tensile strength. Y

16. The invention according to claim 13 wherein at least one of said casings'is provided with means atboth ends to anchor it to a foundation.

17. The invention according to claim 16 wherein said casing adapted for anchoring is positioned at one terminus of said plurality of parallel connected casings.

18. The invention according to claim 13 wherein the uninflated circumference of each said bag at any position along its length is greater than the circumference of its casing at the corresponding position.

19. The invention according to claim 18 wherein said bag material is polyethylene film and said casing material is nylon coated fabric of high tensile strength.

20. The invention according to claim 18 wherein at least one of said casings is provided with means at both ends to anchor it toa foundation.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN INFLATABLE STRUCTURAL MEMBER WHICH COMPRISES AN ELONGATED TUBE MADE OF FLEXIBLE AND SUBSTANTIALLY NONELASTIC MATERIAL WHICH HAS AT LEAST ONE BEND FABRICATED IN ITS LENGTH SUCH THAT SAID TUBE IS EXPANDED IN CIRCUMFERENCE AT SAID BEND, AT LEAST ON THE INNER SIDE THEREOF WHEREAT SAID TUBE DEFINES A CONVEX SURFACE ALONG A PORTION OF ITS LENGTH AS VIEWED FROM WITHOUT, TO THEREBY INCREASE THE BENDING MOMENT CAPABILITY OF SAID MEMBER, WHERE SAID BENT TUBE IS ADAPTED FOR INFLATION TO A PRESSURE SUFFICIENT TO MAKE IT RIGID. 